The devices known hitherto, of the circuit breaker or fuse type, do not allow electrical lines to be cut quickly enough to avoid electrocution or component deterioration. Moreover, their reaction time is too long to provide good protection in the case of a storm for example. Also, these systems protect only certain electrical lines but not the neutral or the ground line.
Other known devices measure a residual current with respect to the ground connection. For that reason, these devices are sensitive to parasites and their triggering threshold has to be high.
Moreover, all the devices quoted above do not reconnect the lines after they are triggered, which can be prejudicial to the operation of alarms, refrigerators, freezers and aquaria during long absences of the user or of the proprietor.